JP7276035B2 - hydrodynamic bearing - Google Patents

Description

The present invention relates to a hydrodynamic bearing.

Conventionally, as a gas bearing, there is known a foil bearing that includes a thin plate-shaped top foil arranged on the outer peripheral side of a rotating shaft and a bump foil arranged on the outer peripheral side of the top foil and elastically supporting the top foil ( For example, see Patent Document 1). In such a foil bearing, as the rotational speed of the rotating shaft increases, air flows between the rotating shaft and the top foil, forming an air film therebetween. The foil bearing supports the rotating shaft in a non-contact state by floating the rotating shaft from the inner peripheral surface of the top foil by the air film. The top foil is pressed toward the outer periphery by the dynamic pressure of the air film, while being elastically supported from the outer periphery by the bump foil. Therefore, the gap between the rotating shaft and the top foil is automatically adjusted according to the rotating speed of the rotating shaft.

JP 2015-194252 A

By the way, in such a foil bearing, in order to stably support the rotating shaft in a non-contact state, it is necessary to maintain an appropriate gap between the rotating shaft and the top foil. However, if the rotational speed of the rotating shaft is too high, the gap between the rotating shaft and the top foil becomes too large due to the increase in the dynamic pressure of the air film, and whirling of the rotating shaft tends to occur. Therefore, there is naturally a limit to the upper limit of the rotational speed at which the rotating shaft can be stably supported.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydrodynamic bearing capable of increasing the upper limit of the number of revolutions at which a rotating shaft can be stably supported.

A dynamic pressure bearing for achieving the above object comprises: a top foil arranged on the outer peripheral side of a rotating shaft; a bump foil arranged on the outer peripheral side of the top foil and elastically supporting the top foil; a housing that is arranged on the outer peripheral side and supports the bump foil, and the rotating shaft is supported by dynamic pressure of an air film generated in a gap between the rotating shaft and the top foil as the rotating shaft rotates. The top foil is provided with a communication hole that communicates the inside and outside of the top foil, and a valve that opens the communication hole by opening in response to an increase in the dynamic pressure. ing.

According to this configuration, when the dynamic pressure of the air film increases as the rotational speed of the rotating shaft increases, the valve element opens in response to the increase in dynamic pressure, thereby opening the communication hole. As a result, since the dynamic pressure escapes to the outer peripheral side of the top foil, it is possible to prevent the dynamic pressure from increasing excessively. As a result, it is possible to prevent the gap from becoming too large, thereby suppressing whirling of the rotating shaft. Therefore, it is possible to increase the upper limit of the rotational speed at which the rotating shaft can be stably supported.

1 is an exploded perspective view showing a rotating shaft, a top foil, a bump foil and a housing separated from each other for one embodiment of a hydrodynamic bearing; FIG. FIG. 4 is a cross-sectional view of the hydrodynamic bearing in a state where the rotating shaft is not rotating; FIG. 4 is a cross-sectional view of the hydrodynamic bearing with the top foil expanded. FIG. 4 is a cross-sectional view of the hydrodynamic bearing in a state where the top foil is in contact with the bump foil; FIG. 2 is an enlarged cross-sectional view of the dynamic pressure bearing centering on the valve; FIG. 11 is an enlarged cross-sectional view of a hydrodynamic bearing according to a first modification; The perspective view of the hydrodynamic bearing of the 2nd modification.

An embodiment of a hydrodynamic bearing will be described below with reference to FIGS. 1 to 5. FIG.
As shown in FIG. 1 , the dynamic pressure bearing 10 includes a cylindrical top foil 20 arranged on the outer peripheral side of the rotating shaft 50 and a cylindrical top foil 20 arranged on the outer peripheral side of the top foil 20 and spaced apart from each other in the axial direction of the top foil 20 . and a plurality of bump foils 30 arranged at intervals and elastically supporting the top foil 20. - 特許庁In this embodiment, two bump foils 30 are provided.

A cylindrical housing 40 that supports the outer peripheral surface of each bump foil 30 is provided on the outer peripheral side of each bump foil 30 . The dynamic pressure bearing 10 of the present embodiment radially supports the rotating shaft 50 in a non-contact state by the dynamic pressure of the air film generated in the gap between the rotating shaft 50 and the top foil 20 as the rotating shaft 50 rotates. It is something to do.

The rotation direction of the rotating shaft 50 in this embodiment is the clockwise direction in FIG. In addition, henceforth, the rotation direction of the rotating shaft 50 is called the rotation direction X. As shown in FIG. Further, the direction in which the central axis C of the top foil 20 extends is called the axial direction, and the circumferential direction around the central axis C is simply called the circumferential direction.

<Top foil 20>
As shown in FIGS. 1 and 2, the top foil 20 is formed by rolling a flexible metal plate material such as stainless steel into a cylindrical shape. A holding end 21 and a free end 22 are provided at one end and the other end of the top foil 20 in the circumferential direction, respectively. The holding end 21 protrudes toward the outer peripheral side and is held by being inserted into a concave groove 41 formed in the inner peripheral surface of the housing 40 . The free end 22 has a gap with the holding end 21 in the circumferential direction. The top foil 20 has a substantially cylindrical shape as a whole. When the rotating shaft 50 is not rotating, the outer peripheral surface of the rotating shaft 50 and the inner peripheral surface of the top foil 20 are in contact with each other.

The top foil 20 is provided with a plurality of valves 23 each having a communicating hole 24 for communicating the inside and outside of the top foil 20 and a valve body 25 for closing and opening the communicating hole 24 . The valve body 25 closes the communication hole 24 and opens the communication hole 24 by opening the valve in response to an increase in the dynamic pressure of the air film. In this embodiment, three valves 23 are circumferentially spaced from each other.

Each valve 23 is provided in a portion of the top foil 20 between the bump foils 30 in the axial direction. One of the valves 23 is provided on the opposite side of the holding end 21 across the central axis C of the top foil 20 .

The valve body 25 is a segment formed in the top foil 20 . Therefore, the valve body 25 is formed integrally with the top foil 20 . The valve body 25 extends from the free end 22 side toward the holding end 21 side along the top foil 20 in the circumferential direction. That is, the valve body 25 extends from the rear side in the rotation direction X toward the front side. The width of the valve body 25, that is, the length in the axial direction is constant in the circumferential direction.

The valve body 25 closes the communication hole 24 until the dynamic pressure of the air film reaches a predetermined dynamic pressure. At this time, minute notches extending along the circumferential direction are formed between both axial end edges of the valve body 25 and the edge of the communication hole 24 . Between the edge of the valve body 25 on the side of the holding end 21 in the circumferential direction, that is, the tip edge and the edge of the communication hole 24, a minute notch extending along the axial direction is formed.

As described above, the valve body 25 opens by deforming toward the outer peripheral side of the top foil 20 starting from the portion of the valve body 25 on the side of the free end 22 in the circumferential direction.
<Bump foil 30>
The bump foil 30 is formed by rolling a flexible metal plate material such as stainless steel into a cylindrical shape. The bump foil 30 is provided at regular intervals in the circumferential direction, and has a plurality of peaks 33 protruding toward the inner periphery, and valleys 34 provided between the peaks 33 adjacent to each other. have. The cross-sectional shape of each peak 33 perpendicular to the axial direction is semicircular. A cross-sectional shape of each trough 34 perpendicular to the axial direction is an arc along the inner peripheral surface of the housing 40 .

The top foil 20 is elastically supported by the contact of the peaks 33 of the bump foil 30 with the outer peripheral surface of the top foil 20 .
A retained end 31 and a free end 32 are provided at one end and the other end of the bump foil 30 in the circumferential direction, respectively. The holding end 31 protrudes toward the outer peripheral side and is inserted and held in the recessed groove 41 of the housing 40 while overlapping the holding end 21 of the top foil 20 . Therefore, the holding end 21 of the top foil 20 and the holding end 31 of the bump foil 30 are inserted into the concave groove 41 in an overlapping state. As a result, the top foil 20 and the bump foil 30 are held in the housing 40 in a non-rotating state. The free end 32 has a gap with the holding end 31 in the circumferential direction. In addition, the free end 32 is configured by one valley portion 34 .

The operation of this embodiment will be described.
As shown in FIG. 2, when the rotating shaft 50 does not rotate, the outer peripheral surface of the rotating shaft 50 and the inner peripheral surface of the top foil 20 are in contact with each other. At this time, the portion of the top foil 20 on the opposite side of the holding end 21 across the central axis C is in contact with the bump foil 30 due to its own weight.

As shown in FIG. 3, when the rotational speed of the rotating shaft 50 increases, the dynamic pressure of the air film generated in the gap between the outer peripheral surface of the rotating shaft 50 and the inner peripheral surface of the top foil 20 increases. As a result, the top foil 20 expands toward the outer periphery due to the dynamic pressure, so that the holding end 21 of the top foil 20 is displaced toward the outer periphery within the groove 41 of the housing 40 .

As shown in FIG. 4, when the rotation speed of the rotating shaft 50 further increases, the top foil 20 expands to the outer peripheral side due to the dynamic pressure, so that the outer peripheral surface of the top foil 20 and the peaks 33 of the bump foil 30 abuts. At this time, each peak 33 is elastically deformed toward the outer circumference. As a result, the bump foil 30 exerts a pressing force toward the inner periphery on the outer peripheral surface of the top foil 20 . Further, a force directed toward the outer periphery based on the dynamic pressure acts on the inner peripheral surface of the top foil 20 . Due to the balance of these forces, the clearance between the outer peripheral surface of the rotating shaft 50 and the inner peripheral surface of the top foil 20 is appropriately adjusted. As a result, the rotating shaft 50 is rotatably supported in a state of floating above the inner peripheral surface of the top foil 20, that is, in a non-contact state.

As indicated by the two-dot chain line in FIG. 5, when the rotational speed of the rotary shaft 50 further increases, the valve body 25 opens, thereby opening the communication hole 24 . As a result, the dynamic pressure escapes to the outer peripheral side of the top foil 20, so that an excessive increase in the dynamic pressure can be suppressed. As a result, it is possible to prevent the gap from becoming too large, so that whirling of the rotating shaft 50 can be suppressed.

Effects of the present embodiment will be described.
(1) The dynamic pressure bearing 10 includes a top foil 20 arranged on the outer peripheral side of the rotating shaft 50, a bump foil 30 arranged on the outer peripheral side of the top foil 20 and elastically supporting the top foil 20, and the bump foil 30. and a housing 40 arranged on the outer peripheral side and supporting the bump foil 30 . The top foil 20 has a communication hole 24 that communicates the inside and outside of the top foil 20, and the communication hole 24 that opens according to an increase in the dynamic pressure of the air film generated in the gap between the rotating shaft 50 and the top foil 20. A valve 23 having a valve body 25 for opening the is provided.

According to such a configuration, the upper limit of the number of revolutions at which the rotating shaft 50 can be stably supported can be increased.
(2) The valve 23 is provided at a portion of the top foil 20 opposite to the holding end 21 across the central axis C. As shown in FIG.

The dynamic pressure of the air film is maximized at a portion of the top foil 20 on the opposite side of the holding end 21 across the central axis C.
According to the above configuration, since the valve 23 is provided in the portion of the top foil 20 where the dynamic pressure is maximum, it is possible to suppress an excessive increase in the dynamic pressure in that portion. As a result, it is possible to effectively suppress the excessive increase in the gap and, in turn, the wobbling of the rotating shaft 50 .

(3) A plurality of valves 23 are spaced apart from each other in the circumferential direction of the top foil 20 .
According to such a configuration, it is possible to suppress an excessive increase in the dynamic pressure of the air film over a wide range in the circumferential direction of the top foil 20 . As a result, it is possible to effectively suppress the excessive increase in the gap and the whirling of the rotating shaft 50 .

(4) The valve body 25 is a segment formed on the top foil 20 .
According to such a configuration, the communication hole 24 and the valve body 25 are formed at the same time by forming the cut in the top foil 20 . Therefore, compared to the case where the valve body 25 is formed separately from the top foil 20, the configuration of the top foil 20 and, in turn, the dynamic pressure bearing 10 can be simplified.

(5) The valve body 25 is opened by deforming toward the outer peripheral side of the top foil 20 starting from the portion of the valve body 25 on the free end 22 side in the circumferential direction.
In the hydrodynamic bearing 10, the rotating shaft 50 rotates along the top foil 20 in the circumferential direction from the free end 22 side toward the holding end 21 side. Therefore, the air flowing into the gap between the rotating shaft 50 and the top foil 20 flows from the free end 22 side toward the holding end 21 side along the top foil 20 in the circumferential direction. This makes it easier for the dynamic pressure of the air film to act on the portion of the valve body 25 closer to the holding end 21 than to the portion closer to the free end 22 in the circumferential direction.

According to the above configuration, the dynamic pressure of the air film tends to act on the tip side of the valve body 25 . As a result, the valve body 25 can be easily deformed toward the outer peripheral side of the top foil 20, and the valve body 25 can be smoothly opened.

(6) A plurality of bump foils 30 are arranged on the outer peripheral side of the top foil 20 at intervals in the axial direction of the top foil 20 . The valves 23 are provided in portions of the top foil 20 between the bump foils 30 in the axial direction.

According to such a configuration, a plurality of bump foils 30 are arranged on the outer peripheral side of the top foil 20 at intervals in the axial direction of the top foil 20 . A valve 23 is provided in a portion of the top foil 20 between the bump foils 30 in the axial direction. Therefore, since the valve element 25 does not interfere with the bump foil 30 when the valve is opened, the formation range of the valve 23 can be expanded in the circumferential direction independently of the bump foil 30 . Thereby, the opening degree of the valve 23 can be adjusted by the dynamic pressure of the air film.

<Change example>
This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

In addition, in the first modification and the second modification shown in FIGS. 6 and 7 below, the same configurations as in the above embodiment are denoted by the same reference numerals, and the corresponding configurations are denoted by "100" and "200". ” is added to omit redundant description.

- It is also possible to arrange three or more bump foils 30 on the outer peripheral side of the top foil 20 at intervals in the axial direction.
・As shown in FIG. 6, one bump foil 130 having the same length as the axial length of the top foil 120 is arranged on the outer peripheral side of the top foil 120, and the peak portion of the bump foil 130 in the circumferential direction A valve 123 can also be provided between 133 .

- The valve body 25 may extend along the top foil 20 in the circumferential direction from the holding end 21 side toward the free end 22 side. In this case, the valve element 25 is deformed toward the outer periphery of the top foil 20 from the portion of the top foil 20 closer to the holding end 21 than the communication hole 24 to open the valve.

The valve may have a pair of valve bodies whose starting points are the edge on the holding end 21 side and the edge on the free end 22 side of one communication hole 24, and whose tips are butted against each other. good.

- The valve body 25 may extend from one side to the other side in the axial direction, or may extend from the other side to the one side in the axial direction.
- In this embodiment, the valve body 25 is formed integrally with the top foil 20, but a valve body that is separate from the top foil 20 and closes and opens the communication hole 24 may be adopted. can also In this case, the valve body may deform toward the outer circumference of the top foil 20 starting from a portion closer to the free end 22 in the circumferential direction than the communication hole 24 .

- The number of valves 23 and the formation position can be changed as appropriate.
- The width of the valve body 25, that is, the length in the axial direction, may increase toward the distal end side, or may decrease toward the distal end side.

- The valve 23 may not be provided on the opposite side of the holding end 21 across the central axis C of the top foil 20 .
• As shown in Figure 7, the top foil 220 may have a plurality of valves 223 axially spaced from each other. In particular, when supporting a rotating shaft 250 having a plurality of herringbone grooves 251 formed at intervals in the axial direction, it is preferable to provide each valve 223 at a portion corresponding to the top 252 of the herringbone groove 251. . In this modification, three valves 223 are circumferentially spaced from each other in the portion corresponding to the top 252 of each herringbone groove 251 . Therefore, in this modified example, a total of six valves 223 are provided. According to such a configuration, it is possible to suppress an excessive increase in the dynamic pressure at the top portion 252 where the dynamic pressure is highest in the gap between the rotating shaft 250 and the top foil 220 . Therefore, the rotating shaft 250 can be stably supported.

DESCRIPTION OF SYMBOLS 10... Dynamic pressure bearing, 20... Top foil, 21... Holding end, 22... Free end, 23... Valve, 24... Communication hole, 25... Valve body, 30... Bump foil, 31... Holding end, 32... Free end, DESCRIPTION OF SYMBOLS 33... Peak part 34... Valley part 40... Housing 41... Groove 50... Rotating shaft 120... Top foil 123... Valve 130... Bump foil 133... Peak part 134... Valley part 220... Top foil, 223...valve, 250...rotating shaft, 251...herringbone groove, 252...top.

Claims (6)

A top foil arranged on the outer peripheral side of the rotating shaft;
a bump foil disposed on the outer peripheral side of the top foil and elastically supporting the top foil;
a housing arranged on the outer peripheral side of the bump foil and supporting the bump foil;
A dynamic pressure bearing that supports the rotating shaft by dynamic pressure of an air film generated in a gap between the rotating shaft and the top foil as the rotating shaft rotates,
The top foil is provided with a valve having a communication hole communicating between the inside and outside of the top foil and a valve body covering the communication hole,
The valve body is a piece formed on the top foil, and is deformed by rocking the piece to open and close the valve,
The degree of opening of the valve body increases as the dynamic pressure increases, and decreases as the dynamic pressure decreases.
hydrodynamic bearing. A top foil arranged on the outer peripheral side of the rotating shaft;
a bump foil disposed on the outer peripheral side of the top foil and elastically supporting the top foil;
a housing arranged on the outer peripheral side of the bump foil and supporting the bump foil;
A dynamic pressure bearing that supports the rotating shaft by dynamic pressure of an air film generated in a gap between the rotating shaft and the top foil as the rotating shaft rotates,
The top foil is provided with a valve having a communication hole communicating between the inside and outside of the top foil and a valve body covering the communication hole,
The top foil is provided with a holding end and a free end held on the inner peripheral surface of the housing at one end and the other end in the circumferential direction, respectively,
The valve body is deformed toward the outer peripheral side of the top foil with a portion of the valve body on the free end side of the top foil in the circumferential direction as a starting point, and the valve is opened from the open state. It deforms to the inner peripheral side and closes,
The degree of opening of the valve body increases as the dynamic pressure increases, and decreases as the dynamic pressure decreases.
hydrodynamic bearing. wherein the valve body is a segment formed on the top foil;
The hydrodynamic bearing according to claim 2 . One end of the top foil in the circumferential direction is provided with a holding end held on the inner peripheral surface of the housing,
The valve is provided in a portion of the top foil on the opposite side of the holding end across the central axis of the top foil,
The hydrodynamic bearing according to any one of claims 1 to 3 . a plurality of said valves are spaced from each other in the circumferential direction of said top foil;
The hydrodynamic bearing according to any one of claims 1-4 . A plurality of the bump foils are arranged on the outer peripheral side of the top foil at intervals in the axial direction of the top foil,
The valve is provided in a portion of the top foil between each of the bump foils in the axial direction.
The hydrodynamic bearing according to any one of claims 1 to 5.

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